Two 15-year-old boys have been convicted of plotting to murder fellow students and teachers at their school.

The teenagers, who were said by prosecutors to have “hero-worshipped” the perpetrators of the 1999 Columbine massacre, were found guilty of conspiracy to murder after planning an attack on their school in Northallerton .

The boys, 14 at the time of the offence, sat motionless alongside their tearful mothers as the verdicts were read out at Leeds Crown Court on Thursday.

During the three-week trial, jurors heard how the boys, who cannot be named for legal reasons, had prepared a “hit list” of people they wanted to kill, including fellow students and teachers who had supposedly bullied or wronged them.

Analysis of their devices showed that they had researched weapons online and had both downloaded a bomb-making manual.

The older defendant, described as the “leader” of the pair, had supposedly “idolised” Eric Harris, who took up arms with fellow teenager Dylan Klebold and carried out a massacre at Columbine High School, Colorado, in 1999, killing themselves and 13 others.

The same boy was later found to have kept a diary in which he espoused what prosecutors described as a “far-right wing ideology” and discussed his motivations for wanting to carry out an attack.

A page from a diary kept by the older boy and a bottle containing flamable liquid that was found by officers searching the older boy's hideout

The pair were questioned by police officers when, in September 2017, the younger boy told a schoolgirl via Snapchat that they were planning to carry out a shooting.

When she asked if he was joking, he responded: “No. No one innocent will die. We promise.”

The next day, he made what the prosecution described as “clear and unvarnished” confessions, firstly to a teacher, and then to police officers.

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Officers searched the boy’s “hideout”, where they discovered a rucksack filled with screws, boards, and a flammable liquid which, prosecutors suggested were instruments with which to build an explosive device.

During the trial, jurors heard extracts from the older boy’s diary which outlined his “twisted ideology”.

A bag of screws that was found by officers searching the older boy's hideout discovered in a rucksack full of equipment (Image: PA)

The inside cover of the book, which was recovered from the teenager’s home in October 2017, reads: “Sorry if this is found I have committed one of the worst atrocities in British history or I killed myself.”

As well as professing his “love” of murderers in the book, the boy also drew a picture of what prosecutors described as the “perfect school shooter”.

In one passage, the boy claimed: “Everyone is filthy and deserve to be shot, including me. I’ll play the role of god and decide who a let live and die.”

Another page is devoted to “stuff we need” in order to execute a school shooting, including napalm, firearms and pipe bombs.

A chat between defendants where the older boy suggests they should 'shoot up the school', left, and Snapchat messages where the younger boy tells a schoolgirl about details of the plan

In other entries, the boy described the human race as a “vile species which needs to die out” and humanity itself as “a curse and a burden”.

A picture of the book was shown to the court with the words “Helter Skelter” written on the cover, a supposed nod to notorious murderer Charles Manson’s idea of an apocalyptic war arising from racial tensions.